Most of the Serpent Society would be random goons except for Viper (obviously) Constrictor (since he's cool) and Cut-Throat (since he's Diamondback's brother). Keep the rest for fights that have multiple goons fighting Cap at once. This could result in some VERY cool fight scenes.

The Serpent Society would be an international narcotics ring who Captain America is dispatched to fight in the city state of Madripoor off the coast of Malaysia.

That said, I still would rather have Zemo and a reformed HYDRA. This time around HYDRA is independent of any nation and wants to overthrow the world to improve it. On some level, this time around Cap might find himself having some level of sympathy towards them even though they're willing to kill innocents to achieve their goals.

Keep in mind that Zemo points out that SHIELD isn't entirely clean either and the main conflict is order vs. chaos.

I hope CA3 involves the replacement Captain America. The writer(s) can update and merge the backstories of John Walker and the ‘Anti-Cap’. John Walker can start off as a 21-ish year old enlisted man, dishonorably discharged after a 3-year stint in the Navy on September 10th 2001 (he was part of a weekend-pass/voucher forging operation). His girlfriend, who had recently quit him, was an intern working in the WTC). Back in his Georgia hometown, Walker is heartbroken, despondent, and rage-filled, he is turned down for reenlistment. He drifts from job to job, usually getting fired after blowing up at someone. 6 months later, he’s embedded with a militia group that’s involved in a plot to blow up a local bridge. As it turns out, the group has been infiltrated by an FBI agent; the agent offers Walker immunity for his cooperation. Walker reluctantly complies, and is in turn confronted by a Navy admiral, who offers him a chance to ‘redeem himself for his country’. Thus does Walker become the volunteer for the ‘super-SEAL’ program. An alternative to the original serum is used, with modern steroids. The ‘US Agent’ was not publicized, a wetwork operative. He has been active throughout the years. When Steve publcly quits SHIELD for a time, Walker is brought in publicly. A new sidekick is brought in (Battlestar). A new villain can be Alexander Lukin, the Kronos corporation. Other options include Dr. Faustus, Cobra, Flag Smasher, etc. I would have Steve become Nomad while he was replaced, then go on his own against the bad guys, eventually coming to blows with USAgent/Anti-Cap and the main villain at the same time.

Okay then Baron Zemo as Bid Bad & even one of the two mentioned as hired help?

I also have gotten to like The Hood but he is less known then the ones mentioned. The Hood has been an enemy to both Avengers & Cap America.

Well Zemo would work and those two would be good henchmen.

I did not like the Hood, at least the way Bendis wrote him, where he seemed like a Mary Sue villain. I didn't buy that all those villains simply deferring to the Hood in Bendis 'Avengers, sure some would, but some like the Wizard would be too arrogant to follow the Hood, while others like Scarecrow and Purple Man would be too crazy to follow orders. Vaughn wrote the Hood better, but Vaughn's Hood would not a be suitable Cap villain either.

Plus Cap should be dealing with international terrorists, not petty street thugs. There is no real dynamic between Hood and Cap to warrant him being in a Cap movie.

Hood honestly will probably pop up in a Luke Cage episode. He works better as a villain for Cage. Cap has enough villains to keep his series going without needing to poach. Also, Wizard is over at Fox.

Well it obviously depends on the fallout from CA:TWS (I've been staying fairly spoiler free on that one), but I'd like to see Sin & Crossbones as the main villains on a quest to resurrect Red Skull. It might make more sense to make Sin the Red Skull's granddaughter in the MCU, but I've always enjoyed the characterizations of her & Crossbones in Brubaker's run. A 'Natural Born Killers' vibe would be an interesting dynamic, especially since it might allow Sharon Carter to take on a larger role as a foil to Sin.

Zemo or Strucker would be good as the modern front for HYDRA also - I like the way they were portrayed in EMH, so there's something to draw from already.